According to Flynn, Hall wanted to train for Boston in a different setting than Flagstaff, Arizona, but remain at high altitude.

“He felt that he could focus and prepare well in that environment for his upcoming marathon,” Flynn said in an email to Runner’s World Newswire.

Hall was supposed to go on a similar training trip to Kenya[10] last year before the Boston Marathon. Injury forced him to cancel the trip, and then to withdraw from the marathon.

Hall was a late addition to the 2014 Boston Marathon[11] men’s elite field. Hall, who has run Boston three times, holds the unofficial American record of 2:04:58, which he set at Boston in 2011. His run at this year's Boston is widely seen as pivotal for his career, as the last time he completed a marathon was January 2012, when he placed second at the Olympic Trials[12]. Hall dropped out of the Olympic Marathon in August 2012, and in addition to not starting Boston last year, withdrew from the 2012 and 2013 New York City Marathon[13].

According to Flynn, the Halls will return to the U.S. shortly before the April 21 race.